This invention relates to a chain V-belt for use on stepless speed variators.
A belt used on stepless speed variators is rubber or metallic, and the belt relating to this invention belongs to the latter, which is a V-belt consisting of a metallic chain. In the chain V-belt, various types are used properly according to a purpose, and the most representative belt comprises a type wherein many a link is arrayed, a pin is inserted at every pitches to flexibility, the pin is brought in contact with a pulley on its both ends, and a predetermined power is transmitted on a frictional force arising between both the two.
A conventional form of the above-mentioned belt is as shown in FIG. 1, wherein a pin 1 with both ends slightly projected comes in contact with inside walls 3, 3 of two-split pulley blocks 2, 2, an interval W between the pulley blocks 2, 2 changes in accordance as one pulley block 2 of the two-split pulley blocks 2, 2 moves horizontally in the drawing, points of contact A, B of the pulley blocks 2, 2 and the pin 1 continuously change radially, of the pulley block 2, namely vertically in the drawing, and thus a power is transmitted in a stepless manner from a driving shaft to a driven shaft. However, a belt 5 contacts with the inside wall 3 of the two-split pulley block 2 at the points A, B theoretically, a normal force T vertical to the inside wall 3 is balanced with a radial component of force Fr of tension working on the belt 5 at the points A, B, however, the normal force T must be increased to enhance a frictional force between both ends of the pin 1 and the inside wall 3 for transmitting a large power, and thus there may arise a case where an exceedingly high pressure works on the points A, B beyond a permissible pressure to withstand. Accordingly, a contact area between the inside wall 3 of the two-split pulley block 2 and the pin 1 will have to be enlarged in such a case.
On the other hand, portions whereat the inside wall 3 of the two-split pulley block 2 and the pin 1 come in contact with each other are the points of contact A, B on both ends of the pin 1, and further the inside wall 3 has a predetermined inclination, therefore a push force P from each of the pulley blocks 2, 2 works radially outside of a center line C--C of the pin 1, namely radially outside of a tension line working on the belt 5, thus the belt 5 is spoiled for nip force to the pulley block 2 and hence for normal tightness with the pulley block 2, and the belt 5 is capable of slanting during use.
Then, in U.S. patent specification U.S. Pat. No. 4,349,343, there is disclosed an apparatus wherein a cylindrical block (referred to as "drive pin" in the specification) is provided in the form of offsetting inward or outward to the pin other than a pin coupling the links, an end of the block and an inside wall of the pulley are brought in contact with each other to transmit a driving force. In the apparatus, however, while a push force can be made to work effectively on the block by positioning the block radially inside of the pin, the block is circular in section as in the case where the pin shown in FIG. 1 is used to serve as the block at the same time, a contact length with the pulley block inside wall 3 is equal to the diameter D even at maximum accordingly, but actually the end is conical in shape, therefore the contact length is 1/2 of the diameter. On the other hand, the pulley block inside wall 3 is curved to a link straight line based on the chain V-belt as shown in FIG. 8, therefore a block 13 to transmit a power in contact with the pulley block 2 comes in contact with the pulley block inside wall 3 at points P1, P1, therefore to transmit the power more efficiently, it is preferable that the block 13 come in contact with the inside wall 3 at a maximum contact line L1 passing the center as shown in FIG. 2, however, it shifts somewhat horizontally in the drawing actually according to a state at the time of contact. In the case of a block 13' circular in section as shown in FIG. 2, the length of a contact line L2 suddenly decreases in accordance as the contact line moves horizontally in the drawing to the maximum contact line L1, and further in the case of a block 13" conical in the end surface as shown in FIGS. 3 (a), (b), it decreases suddenly furthermore, a surface pressure between the block and the inside wall 3 rises, the block is thus worn out one-sidedly or oscillates heavily to give rise to noise, and further a life of the V-belt deteriorates in consequence. It is then necessary to enlarge the diameter D of the blocks 13', 13" for making the contact line longer, however, since the blocks come inside of the pin, there may arise an interference between adjacent blocks or the block and the link. Further, in the case of the above-mentioned U.S. patent specification, the blocks 13', 13" are fitted in slidably to the links and circular in section in addition, therefore the blocks slide and turn at every junctions to the pully block 2, a block fitting hole is thus worn out so early, a life of the belt deteriorates, and oscillations to arise are capable of spoiling a correct transmission operation consequently.